Electrical apparatus



L. O. GRONDAHL ET AL ELECTRICAL APPARATUS Filed May 1'7, 1929 April 21, 1931.

Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE LARS O. GRONDAHI, OF PITTSCBURGI-I, ANI) DONALD G. AG'KER-LY, OF EDGEWOOD, .TE'ENN- SYLVANIA, ASSIGNOB-S T0 THE UNION SWI'ICH & SIGNAL COMPANY, OF SWISSVALE, PE'NNSYLV'ANIA, A CORPORATION O]? SPENN'SYLVALN'IA ELECTLRIOAL APPARATUS Application fi1ed May 17,

Our invention relates to clectrical apparatus, and particularly 1:0 apparatus f0r supplying a load with unidirectional current from a source 0f altcrnating current through a rcctifying device.

One object 0f 0ur invention is the provisio'n, in apparatus 0f the type described, of means for disconnecting tl1c source cf alternating current from the rectifying clevice if thc temperature of the rectifying device bec0mes excessive.

We Will describe one form 0f apparatus emboolying our invention, ancl Will then point 0ut the novel features thereof in claims.

The accompanying drawing is a view, partly diagrammatic, and partly cross-scctioned, showing 0110 form 0f apparatus embodying our invention.

Referring to the drawing, the refcrcnce chamcter R designatcs, in gcncral, a rectifying device which in ehe form he1e shown consists of tw0 full wave rectifiers A und A connected in multiple. Each full wave rectifier is made up 0f a plurality of asymmetric units E, each comprising a flat clisk 30 0f mctal, such as copper, having a coating 31 of a comp0und 015 the mctal, such as cuprous oxide formed thereon. As is well known, units of thc typc described exhibit the characteristic of offering a lower resistance t0 currcnt which tends t0 flow from the oxide t0 the copper than 130 current flowing in thc opposite direction.

Thc units E comprising the rectificr A are assemblecl 0n a holt B, which passes through suitable openings in the units, but which is separatecl from the units by a sleeve 26 of insulating matcrial. In similau manncr, thc units E comprising the rectifier A are asscmblecl 011 a holt B, which passes through suitablc openings in tl1c units, and which is separatcd f10m theunits by a slceVc 27 0f insulating material. Adjacent the oxide coating 31 0f each unit E in both rectifiers is placecl a thin layer 28 0f an impressionable conducting material, such for example as lead foil. Intcrposed at suitable intervals in rectificr A arc a plurality 0f metal washers a, b, c, j, k, and m,

1929. Serial N0. 363,851.

which servc as terminals for the rectificrs. Similar metal washers, n, v, p, g, s, t, anal u are insertecl a1; intcrvals in rectifier A. The rectificr A is cliviclecl into f0ur sections 32, 33, 3 l, anal 35, ancl Ehe rectificr A i.s diviclccl int0 f0ur similar sections 322 349, ancl 35K Eacl1 scction constitutes 0110 leg of a full wzwe rectifier, und euch 00mprises, as l1erc shown, four units in scrics. Pressure is appliccl t0 rcctifier A by means of a nut D screwecl on bolt B, und pressurc is appliecl t0 rectifier A" by means cf a nut D scrcwed 011 holt B. Interposed 0ctwecn tl1e hca.d C 0f thc bolt B ancl onc eud of rectifier A is a spring washer J und an insulating washcr H, und intcrposecl between thc nut D ancl the o;her cncl cf rccti* fiel A is a spring washer F anal an insulating washcr K. In si1nilar manner, interposed between tl1e heacl C of thc bolt B, und 0nc encl of rectificr A .is a. spring washcr J anal an insulating washer H, an l intcrposecl between thc nut D anal the other cncl 0f rectifier A is a spring washer F and an insulang washer K Thc insulating wash e1s H, K, H und K" servc t0 insulac "ehe encls 0f Elle rectifiers ff101n tl1e bolts, while the spring Washcrs J, F, J and F tencl t0 maintain a uniform pressurc 0n 'l3l16 rectifiers. Tl1e rectifying clcvice R may bc usccl t0 supply unidirectional currcnt t0 a l0acl from a, s0urcc cf alternating current. As he1e shown, the rectifying clevice R is arrangecl to sugply unialircctional current t0 a direct currcnt n10t01 M f10m ehe seconclary 3 0f a, transformcr T, the primar 1 1 0f which is ab times connectecl witl1 an alternator G over a switcl1 S. l Vhcn switch S is closecl current fi0ws, cluring half cycles 01 onc polarity, frcm seconalary 3 0f transformcr T, tl1rough wire 4%, back conmct 5 of a relay U, wires 6 und 7, mctal washer 70, scction 34t of rectifier A, mccal washer j, wires 8 und 9, m0t0r M, wircs 10, 11, 12 ancl 13, metal washcr a, section 32 cf rectifier A, 1netal washer Z), ancl wires 15 am]. 16 back 130 seconclary 3 cf transformer T. lt Wlll bc sccn filmt scctions 3% und 32 of rcctlficr A are ccnncctecl in parallel with sections 34 und 32 of rectifier A, so that uncler tlxc conditions just escribcd currcnt also fiows from scconc1ary 3 5 transformer T, through wire 4, back c0ntact 5 0f re1ay U, wircs 0 anal 7 metal washcr z, secti0n 0f rectifier 1119'E2L1 Washer s, wires 3, 19 and 9, arnmturc 03": mot0r M, wircs 10, 11, 12 und 13, metal wasncr n, scction 3:2 01 rectificr A, m0tal washer 0, 21m1 wiress 15 anal back t0 sccondary 0i5 nsformer T. During half: cycles 0f the oppositc polarity, currcnt fiows from scc0nary 3 01 transf01mer T thr0ugh wirc 16 und 15, mctal wacher 0, section 33 0'f rectificr A, meta1 washer c, wircs 17, 13, 19 und. 9, mmaturc 01 m0t01* M, Wi10 10, metal wacher m, section 01" rectifier A, mctal vmshe1 7a, wircs 7 anal 0, back c0ntact 5 cf 1*e1ay U, and wire 1 back t0 .scc0nf j 3 01; tiansformer T. At t110 smne timc, current fiows 11'0111 sec0ndzuy 3 0f transf0rsncr T t1-r0ugh wires 16 and 1eta1 v; aber 1), scction 013 rectificr A, mctal washcr p, wir-- 17, armature 0t m0t0r M, Wl 10, 11 und 11, metal wacher M, scction 0' rcctifier A, metal washer f, wires 0110 0, back 0011* tact 5 01": relay U anr1 .xi10 et ack t0 sec0ndary 3. 1Vhcn switch 00(1, thcrcfore, mot0r M is supp1icd with unic 18, 19 and 9,

rccticnal cmrent which 0pemtcs thc 1110t0r. Motor M may be used to contro1 any suitable apparatus not sh0Wn in thc drmving.

VVhen current is supplicd to a load through a rectifying devicc 0f thc type describcd, hcat is deve1oped in the rcctiiying device due 1 0 its resistance, and the temperature 0f the device rises. T110 temperature 01 the 0.cvice continues t0 risc until the rate at which haut is dissipated by the device is equal t0 the rate at which heat is devclope in the device. It is sometimes dcsirablcto supply a comparatively lauge currcnt intermittently to a load through a rectifying dcvice 0f the type desc1*ibec1. This currcnt normally does not flow long enougn to overheat the rectifying device, but if the pcriod 0f time during which this current flows is prolongcd for any reason, or if the amount 0f the current fiowing through thc rcctifying dcvicc is increased above thc normal valuc, thc rectifying device might b0c01110 overheatcd. If the temperaturc 0f th0 device becomcs t00 high, thc rectifying dcvice might bc damaged. T0 prevent the rectiiying device fr01n bccoming t00 hot, we providc mcans for cnergizing relay when the 'tempcmture o1 thc device reaches a predctcrniinec1 va1ue which is below thc valuc necessary t0 damage the rectifying device. As here shown, we have inserted in rcctificr A? two resistancc units zmd 37, which am separat-3d by a thin disk 38 0f some matcrial, such as mica, having high cl0ctri-cal resistan0c but the heat conductiv= ity 0f which is g0od Whcn comparcd with its clecrical conductivity. Metal washers are placcd ajacent units 36 und 37 t0 familitate c1ectrical connection therewith. Thc units 36 and 37 hzwe a high negative temperaturc cocfficient cf resistance, und nmy fo1 example be asymmetric units which arc sinni- 1a.1 t0 tue asymmctric units E already (10- scribcd. Furthcrmorc, wc interpose in rectifier A an auxi1iary rectifier P compris ing f0ur additional asymmctric units E, E", E and E which are simi1ar to asymmetric units E and meta1 contact washers d, e, f, g and h. The rcctifier P is insulated from rcctificr A by tw0 e1cctro-insulating heat conducting c1is1:s 39 anti 4-0, which arc simi- 1arto thc isk 38 c1cscribc above. The auxilizu*y 10ctific1 P, anal the rcsistancc units 30 an 37 are inclu1cd in a circuit f01 relay U. Nhcn switch S is closed, current flows during half cycles 0f onc polarity, from scccndary 2 cf transformcr T through wire 20, m0t211 washer c, asymmetric unit E mcta1 washer (Z, wires 21 und 22", mctal washer 'r', rcsi tance unit 37 in the high resistancc di- 1'8C1310L, mctal vrasher s, wircs S, 18 und 17 mctal was 1e1p,rcsistanccullit 36 in thchigh mistance dircction, nwtal wacher q, wire 23, winding 0:5 rclay U, wire 2-1, mcta1 washcr f, asymmetric unit E mctal washcr g und wirc 25 back to scconda1y 2 0f transformer T. During half cyc1es of the opposite po- 12uity current f'i0ws frcn1 sccondzu:y 2 of transformcr T through wirc 25, meta.l washcr g, asymmctric unit E, metal washer 7a, wires zmd 522", metal washer 0*, resistancc unit 37 in the high rcsistuncc direction, n1etal washer s, wircs 8, 18 und 17 mctal washcr p, rcsistzmcc unit 36 in the high 1'0- sistancc dircction, mctal washcr q wirc 23, winding cf rclay U, wirc .26L, 1nctal washer f, asymmctric unit E", 1116132L1 washcr e, and wire 20 back t0 secondary 2.

The operation cf the apparatus is as follows VIhen switch S is closed unidirectional currcnt is supplied t0 motor M f10111 secondary 3 01" transformer T through rcctificrs A and A connectcd in multiple, and current is also sup;lied to re1ay U from secondary 2 0f transformer T through auxili2uy rcctifier P anc1 rcsistance units 36 und 37. T110 units 36 und 37 arc in good thermal connection with the rast cf thc units in rectifier A1, and it 'E0110Ws that thc units 36 und 37 W11 have approxima-tcly the san1e tempcrature as thc rast 01"? th0 units in rectific r A. The parts a1c prcportioned in such manner that as long as the rcctifiers a1e bclow a prcdetermincd tcmperaturc which is lcss than that W111C11 wou1d damage the rectifiers, the current supplied t0 relay thr0ugh units 36 and 37 is n0t su1"ficient t0 gick up re1ay When the tcmpemture 01 rectifier A becomes excessive, howevcr, thc resistances of the units 36 und 37, through Whi0h the C11116I1b flows in the high resistancc dircction, arc reduced to such an extent,

that the current now supplied to relay U picks up tl1e relay. Contact 5 of the relay is then opened, and secondary 3 0I" transformer T is disconnected from the reetifying device. The secondary 8 0f. transformer T Will remain disconnected from the restlfying clevice until the rectifiers A ancl A have coolecl t0 the temperature at which tl1e resist-ance of units 36 and 37 becomes sulficiently hlgh 130 cause relay U t0 open. Vhen this occurs seconclary 3 of transformer T is again connectecl to load M tl1rougl1 rectifiers A anal A in multiple, and if switch S is still closecl, the l0acl Will be supplied with unidirectional current until the temperature 0f the rectifiers A ancl A again becomes excessive.

The auxiliary rectifier P is placecl in rectifier A t0 get more constant operation. Tl1e output 0f the auxiliary rectifier changes slightly with temperature, ancl iI tl1e units 0f tl1e auxiliary rectifier were placecl outsicle the main rectifier, the temperature at which relay U woulcl close woulcl depencl to s0me extent upon the ambient temperature. By placing tl1e auxiliary rectifier P in the rectifier A, tl1e temperature 0f rectl fier P Will stay at approximately tl1e same temperature as rectifier A. Ractlfier A is similar t0, operates in multiple witl1, rectifier A, anal canies approximately tl1e same loacl, so that the temperature 0f rectifier A Will be nearly the same as the temperature 035 rectlfier A. It follows tl1at rectifier P Will have approximately the same temperature as rectifier A The temperature at which relay U closes is clepenclent upon the temperature of rectifier A", and since rectifier P stays at approximately the same temperature as rectifier A lt follows that with rectifier P mounte l in rectifier A, the temperature at whicl1 relay U Will close is inclepenclent 0f the ambient temperature.

Nhile we have shown the rectifying clevice E as comprising two rectifiers A und. A" 0ne 01 more rectifiers might just as easily be usecl, rlepending upon the conclitions. If one rstifier only is usecl, both the auxiliary rectifier P, ancl the units 36 ancl 37 would tl1en los assemblecl in tl1e one rectifier. "Wl1en more rectifiers are usecl, resist2mce units 35 ancl 37 migl1t also be assemblecl in eacn rectifier. Furthermore, only 0ne resistance unit migl1t be usecl when (l e sirecl, 0r a number 0f resistance units 86 anal 87 cozmectecl in saries 01 in multiple migl1t be usecl. In sonne instances, a number of resistance units mignt be located at different locations in tl1e same rectifier to insure against one portion 0f tl1e rectifier being excessively l1eatecl.

Although we have herein shown and clescribeal 0nly one form 0:" electrical apparatus emboclying' our invention, it is understoocl tl1at vario1is clmnges ancl moclifications may ba made tl1ereln wlthin the scope 01" Ehe appenclecl claims wlthout clepurting from the spirit anal sc-ope of our invention.

Plaving tllus des 'llb8Cl our invention, what WG claim ls:

l. In combination, (l first asymmetric mit, 21 secon l asymmetric unit having; a l1igl1 11eg2.tlve ten1perature coefilc-ient 01" reslstan0e 2111(l ass clatecl with saicl first unit mit in tl1e higl1 resistance clirecti0n clecreases below a precleterminecl value, a loacl, anal means con-trollecl by said contact f01 supplylng saicl loacl witl1 current througl1 saicl first unit.

2. 111 combination, a rectifying devlce comprlsing plurality of asymmetris units,

load, a source 01" alternating cu1re1lt C011- nectecl with Sl(l loaal through saicl rectifying dsvice, rasistance uralt having a higl1 negative ten1peratm*a coelficient of resistance anal interposetl between two acljacent asymmetrric unlts 01" said clevice in g0od heat t1ansferring relation, ancl means Controllecl b sai resistance unit fOI disconnecting sL :rce from said loacl if tl1e seid rectifying device betemperat U 0f c0-mes excessive.

3. 111 combinatlon, a rectifying clevice c0m rising two asymmetric units connectecl in mt"t1ple, auxillary rectifier in goocl heat transiering relation with 0ne 0f saicl asymmetrlc units a resistance unit having a high negative temperature coefilcient 0f resistanc in goocl heat transferring relati0n with the othar of sai :l units, a relay, means i0r supplying saicl relay with eurrent tl1rough saicl auxiliary rectifier and saicl resistance unit, a loacl, ancl means C011- trolled by saicl relay for supplying saicl loacl Wltl1 current through said rectifying clevice.

t. In combination, a rectifying device comprising a plurality of asymmetric units arranged t0 provicle full wave rectification, load, a contact, a s0urce 0f alternating current connectecl witl1 saicl l0acl through S2Ll(l contact anal saicl rectifying clevice, im auxiliary rectifier in 00cl l1eat transferring relation with sai l rectifying device but electrlcally lnsulatecl therefrom, a resistance unit in g00d l1eat transferring relation wlth salcl rectifying levlce but electrically insulatecl therefrom anal l1aving a high negative temperature coeficlent 0f resistance, a wintling f0r controlling saicl contact, and means for supplying saicl Winding with cu rrent tl1rougl1 saicl auxiliary rectifier anal Sind asymmetric unit.

5. In combination, a rectifying clevice comprlsing t*vo full wave rectifiers (3011- .nectecl in multiple, an auxiliary rectifier in gootl thermal connection with one of said rectifiers, a plurality 0f resistance units in good thermal connection with the other of said rectifiers and each having a high negative temperature coefficient 01 resistance, a soure of alternating current, a relay C011- nected with said source through said resist ance unis in series und througn said auxiliary rect-ifier, a l0ad, and means controlled by said re1ay for at times connecting said source Wi'ah said load through said rectify" ing device.

In testimony whereof WG aflix 0ur signatures.

LARS O. GRONDAHL.

DONALD G. ACKERLY. 

